1.) Telegram offers end-to-end encryption and have a 'Secret Chat' feature, that self-destruct messages after the conversation. The company is offering $200,000 Prize in Bitcoin to the first person to crack its Encryption.
"We support two layers of secure encryption (server-client and client-client). Our encryption is based on 256-bit symmetric AES encryption, RSA 2048 encryption and Diffie–Hellman secure key exchange." Company states on their website.

2.) Surespot allows you to send and receive text messages, pictures and audio clip with end-to-end encryption. It uses 256 bit AES-GCM encryption using keys created with 521 bit ECDH which can only be decrypted by sender and receiver.
Unlike WhatsApp, if you delete a message, it's deleted from the recipient's phone, too. Surespot supports multiple identities on a single device. Download Surespot for Android and iOS.

3.) Threema is not free, but a perfect alternate for WhatsApp, use end-to-end encryption and gives you all features of WhatsApp like text messaging, image sharing, and voice chat as well.

4.) TextSecure and 5.) RedPhone also provides end-to-end encryption for messaging and voice calls respectively. RedPhone allows you to upgrade a normal call to secure call whenever it senses the possibility to fulfil the requirements.